Running 12.04 LTS using a Centrino Advanced-N 6200 wireless card. This solution work for me as well. Not thrilled I can't run N, but at least when I use other wireless hotspots I can at least connect. Edit /etc/modprobe.d/iwlwifi.conf

I was able to get my Centrino Advanced-N 6200 to work by disabling N mode on my wifi router. This is not an ideal solution seeing as I'll be roaming on wireless networks that I can't control. It seems there are ways to disable N mode on the wifi card itself which may also work.